Many processes are available for the converions of the various fractions of crude oil to transportation and heating fuels. These processes include alkylation, polymerization, reforming, hydrocracking and fluid catalytic cracking. The technology of fluid catalytic cracking (FCC) has evolved around the process of cracking feedstocks boiling below 1050.degree. F., commonly referred to as atmospheric and vacuum gas oils (VGO), in the absence of added molecular hydrogen and at low pressures below 50 psig. The gas oil feedstocks contain low, if any, concentrations of coke precursors such as asphaltenes, naphthenes and porphyrins to provide a Conradson carbon below 0.5 wt% and contaminant metals (Ni-V-Cu-Na), below 0.2 ppm by weight. However, the availability of select crudes that contain a high percentage of clean gas oils has diminished and have been replaced by crude oils containing higher percentages of 1050+ material containing high concentrations of Conradson carbon producing materials and contaminant metals. The materials known as reduced crude, topped crude, atmospheric tower bottoms and the like, essentially boil above about 650.degree. F. and contain material boiling above 1050.degree. F., whose endpoint can be as high as 1500.degree.-1700.degree. F. Thus, a reduced crude with vacuum tower bottoms contains all of the Conradson carbon and contaminant metal values as opposed to atmospheric and vacuum gas oils which generally contain a trace of these materials depending on crude source.
Petroleum refiners have been investigating means for processing reduced crudes, such as by visbreaking, solvent deasphalting, hydrotreating, hydrocracking, coking, Houdresid fixed bed cracking, H-oil, and fluid catalytic cracking. One or more approaches to the processing of reduced crude to form transportation and heating fuels is that described in copending applications, U.S. Ser. Nos. 904,216 (now U.S. Pat. No. 4,341,624); 904,217 (now U.S. Pat. No. 4,347,122); 094,091 (now U.S. Pat. No. 4,299,687); 094,227 (now U.S. Pat. No. 4,354,923) and 094,092 (now U.S. Pat. No. 4,332,673) which are herein incorporated by reference thereto.
In the operations of the above identified applications, a reduced crude is contacted with a hot regenerated catalyst in a short contact time riser cracking zone, the catalyst and products are separated instantaneously by means of a vented riser to take advantage of the difference between the momentum of gases and catalyst particles. The catalyst is stripped, sent to a regenerator zone and the regenerated catalyst is recycled back to the riser to repeat the cycle. Due to the high Conradson carbon values of the feed, coke deposition on the catalyst is high and can be as high as 12 wt% based on feed. This high coke level can lead to excessive temperatures in the regenerator, at times in excess of 1400.degree. F. to as high as 1500.degree. F., which can lead to rapid deactivation of the catalyst through hydrothermal degradation of the active cracking component of the FCC catalyst (crystalline aluminosilicate zeolites) and unit metallurgical failure.
As described in the above mentioned co-pending reduced crude patent applications, excessive heat generated in the regenerator is overcome by heat management through utilization of a two-stage regenerator, generation of a high CO/CO.sub.2 ratio to take advantage of the lower heat of combustion of C to CO versus CO to CO.sub.2, low feed and air preheat temperatures and water addition in the riser as a catalyst coolant. As described and taught in these applications water is added to the feed prior to contact with the regenerated catalyst and the carbo-metallic feedstock-catalyst mixture is benefited in several respects. These benefits include some catalyst cooling, generation of steam for aiding feed dispersion, lowering of feed partial pressure and assisting as a transport lift gas. This mixing of water and carbo-metallic oil does not necessarily produce the ultimate desired effect of feed dispersion through small droplet size formation (misting) and, better and more consistent catalyst cooling through better contact of catalyst and water droplets. Therefore, a much better method of dispersion of carbo-metallic oil with water is desirable to achieve more complete, consistent and intimate catalyst-water contact with carbo-metallic oil dispersion into very fine droplets to provide a more intimate catalyst-oil contact in the riser.